Erik Jones <erik(at)myemma(dot)com> writes:
> We've recently made a couple changes to our system that have resulted
> in a drastic increase in performance as well as some very confusing
> changes to the database statistics, specifically
> pg_stat_database.xact_commit. Here's the details:
I'm kinda boggled too. I can see how increasing shared buffers could
result in a drastic reduction in write rate, if the working set of your
queries fits in the new space but didn't fit in the old. I have no idea
how that leads to a drop in number of transactions committed though.
It doesn't make sense that autovac would run less frequently, because
it's driven by number of tuples changed not number of disk writes; and
that could hardly account for a 10x drop anyway.
Did you by any chance take note of exactly which processes were
generating all the I/O or the CPU load?
regards, tom lane